A TV broadcasting provider sets up and operates transmitters and repeaters according to the broadcasting service coverage of a broadcast station or the natural environment in the broadcasting service coverage to provide a broadcasting service. A repeater is set up in a shadow region where signals are weakly received to solve the problem of unstable signal reception and extend the transmission range of broadcasting signals transmitted from a main transmitter.
Until now, a terrestrial digital TV broadcasting service according to the Advanced Television System Committee (ATSC) as well as an analog TV broadcasting service is provided through a Multiple Frequency Network (MFN) which is formed allocating a different frequency to each transmitter or repeater. However, since building the multiple frequency network does not allow reusing the same frequency in neighboring areas except for a long distance area, it is inefficient in view of using frequency resources.
This calls for the development of a Single Frequency Network (SFN) that can increase utility efficiency of broadcasting frequency by using the same frequency band in multiple transmitters/repeaters and secure stable power strength within a broadcasting service area. Also, insufficient broadcasting frequency resources allocated to transmitters and repeaters for each broadcast station requires the development of the single frequency network in the circumstances that a terrestrial analog TV broadcasting service and a terrestrial digital TV broadcasting service are provided at the same time.
Technology for configuring a single frequency network includes Digital On-Channel Repeater (DOCR) technology, Distributed Transmitter (DTxT) technology, and Distributed Translator (DTxR) technology in a terrestrial digital TV broadcasting based on the ATSC. According to the DOCR technology, transmitters and repeaters use the same frequency. According to the DTxT technology, the same frequency is used during transmission. According to the DTxR technology, the same frequency is used during repeating. Hereafter, the DOCR technology and the DTxR technology will be described with reference to the accompanying drawings.
FIG. 1 illustrates the DOCR technology.
Referring to FIG. 1, a main transmitter 101 transmits a broadcasting signal through a frequency A. Repeaters 102, 103, 104 and 105, which transmit the broadcasting signal in the same channel that the main transmitter 101 uses, receive the broadcasting signal transmitted from the main transmitter 101 and repeat the broadcasting signal using the same frequency A that the main transmitter 101 uses. Since the DOCR technology requires high isolation between transmission and reception antennas, conventional equipments can be hardly used and thus a great deal of investment is required.
FIG. 2 illustrates the DTxR technology.
Referring to FIG. 2, a main transmitter 201 transmits a broadcasting signal through a frequency A. Repeaters 202, 203, 204 and 205 repeat the broadcasting signal in a frequency B which is different from the frequency A.
When the single frequency network is configured based on the DOCR technology, the DTxT technology or the DTxR technology, the frequency utility efficiency may increase but interference is caused between a transmitter and a repeater or between repeaters or transmitters due to the use of a single frequency. This problem may be solved by controlling transmission powers and timings of each repeater or transmitter in the broadcasting network. Transmitter Identification (TxID) having excellent correlation characteristics is assigned to each transmitter or repeater in order to facilitate the control of the broadcasting network based on the ATSC Recommended Practice (RP) A/110. The assigned TxID is added to a transmission signal or a repeat signal and then transmitted out. The broadcasting is readjusted by measuring reception characteristics caused in transmission channels between transmitters and receivers, or between repeaters and receivers through a TxID signal analyzer based on the ATSC RP A/111.
According to the method for readjusting the broadcasting network, reception characteristic information of a non-signal reception area among areas where a signal of a main transmitter and/or a repeater, or signals of main transmitters and/or repeaters are overlapped is analyzed and power or transmission time of the signals transmitted from a main transmitter and/or those from a repeater is adjusted based on the analyzed reception characteristic information. Broadcasting reception condition of the non-signal reception area may be improved by adjusting the power or the transmission time. Meanwhile, a signal receivable area where signals can be received may turn into a non-signal reception area, or the broadcasting signal reception condition of the signal receivable area may become poor. Since a reception sensitivity should be measured for each field individually and manually to minimize the non-signal reception area, it takes a great deal of time and costs to build and maintain a broadcasting network.